共查询到20条相似文献,搜索用时 62 毫秒
1.
The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths.
Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing
is fixed by known G/ψ−η
c(1S), ψ(2S)−η
c′(2S) splittings, which appears to be small, r
ss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed
in bottomonium. For nS b
states (n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3S and 4S charmonium states, the splittings 16(2) and 12(4) MeV are obtained.
The text was submitted by the authors in English. 相似文献
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S. P. Baranov A. V. Lipatov N. P. Zotov 《The European Physical Journal C - Particles and Fields》2011,71(4):1631
We investigate the inclusive photoproduction of J/ψ mesons at HERA within the framework of the k
T
-factorization QCD approach. Our study is based on the color singlet model supplemented with the relevant off-shell matrix
elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon
contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS
collaborations. Special attention is put on the J/ψ polarization parameters λ and ν, which are sensitive to the production dynamics. 相似文献
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6.
Bastian Kubis Sebastian P. Schneider 《The European Physical Journal C - Particles and Fields》2009,62(3):511-523
Strong final-state interactions create a pronounced cusp in η′→η
π
0
π
0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of π
π scattering lengths from K→3π decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the π
+
π
− threshold. 相似文献
7.
O. A. Savinskaya A. P. Nemudry A. N. Nadeev S. V. Tsybulya N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1053-1054
The structure of high-temperature SrFe1 − x
Mo
x
O3 − z
(0 ≤ x ≤ 0.5) phases was studied. Such studies are necessary to understand the mechanism of oxygen transport in membrane materials
used for high-temperature oxygen separation. 相似文献
8.
G. M. Abramova G. Petrakovskiy R. Zuberek A. Nabialek M. Boem V. Sokolov A. F. Bovina 《JETP Letters》2009,90(3):207-210
The magnetostriction of Fe
x
Mn1 − x
S (x = 0.27) single crystals in strong magnetic fields up to 120 kOe has been investigated. It has been found that the magnetostriction
reaches colossal values (±3 × 10−4) atypical of compounds of 3d elements. It has been found that the magnetostriction changes sign when varying temperature and magnetic field; this behavior
indicates an important role of the spin-phonon interactions in the formation of the magnetic order in solid solutions of iron-manganese
sulfides. 相似文献
9.
Om diagnostic is a good geometric method to differentiate one dark energy model from LCDM. We apply three different two-parameter
equation of state ω
σ
(EOS) to Dilaton Dark energy (DDE) model and investigate the Om diagnostic for these cases. We obtain that DDE model can be easily distinguished from LCDM no matter which case is considered.
We also investigate the influence of coupled parameter α on the evolutive behavior of Om−z. According to the numerical result of Om, we get the current value of equation of state ω
σ0=−0.939 which fits the observational data well. 相似文献
10.
B. Song Y. Yong J. Hou P. He 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):399-406
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to
calculate the structural and electronic properties of
Si
n
C
n
(n = 10–15) clusters. We find that the Si
n
C
n
clusters prefer cagelike structures. An extensive isomer search shows that the lowest-energy arrangements are those in which
the silicon atoms and the carbon atoms form two distinct subunits. It is found that the carbon atoms favor to form fullerene-like
structure due to the
sp
2-like bond. The silicon atoms are trying to cope with an unfavorable
sp
2 environment, but distorted tetrahedra still show up somewhere of the cagelike structures. On the basis of the lowest-energy
geometries obtained, the binding energy, HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity of the
clusters have been computed and analyzed. An electronic charge transfer from the Si-populated to the C-populated regions is
observed. 相似文献
11.
A. Polishchuk 《Communications in Mathematical Physics》2004,247(3):527-551
The main result of this paper is the proof of the transversal part of the homological mirror symmetry conjecture for an elliptic curve that states an equivalence of two A-categories: one is built using holomorphic vector bundles on an elliptic curve and another is a subcategory in the Fukaya A-category of a torus. The proof is based on the study of A-structures on the category of line bundles over an elliptic curve satisfying some natural restrictions (in particular, m1 should be zero, m2 should coincide with the usual composition). The key observation is that such a structure is uniquely determined up to equivalence by certain triple products.This work is partially supported by NSF grant 相似文献
12.
The rare decay \(B\rightarrow {K^{*}}\ell ^+\ell ^-\) is a very significant mode to search for physics beyond the Standard Model (SM). The mode provides a very rich spectrum of observables obtained from the angular distribution of its decay products. The recent LHCb measured values of these observables are used to conclude an evidence of right-handed currents at the kinematic endpoint of this decay mode. As the conclusion is drawn at the maximum dilepton invariant mass square (\(q^2\)) kinematic endpoint, it relies only on heavy quark symmetries where it is valid without significant corrections. 相似文献
13.
The process γ*γ → σ is investigated in the framework of the SU(2)×SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ* in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ*γ → π form factor. 相似文献
14.
A. K. Chaudhuri 《The European Physical Journal C - Particles and Fields》2009,61(2):331-338
In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy,
GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T
J/ψ
. Sequential melting of charmonium states (χ
c
, ψ
′ and J/ψ), with melting temperatures
, T
J/ψ
≈2T
c
and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ
p
T
spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts
the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ
p
T
spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,
GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ
p
T
distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC. 相似文献
15.
T. Aliev V. S. Zamiralov S. N. Lepshokov A. Özpineci S. B. Yakovlev 《Physics of Atomic Nuclei》2007,70(5):925-937
New relations between Borel QCD sum rules for the strong couplings of baryons to kaons are derived. It is shown that, on the basis of the sum rules for the coupling constants g πΣΣ and g πΣΛ, the corresponding sum rules can be directly obtained for the coupling constants g KYN and g KYΞ, Y = Σ,Λ. The values of these coupling constants are calculated in the fiducial interval 1.0 ≤ M 2 ≤ 1.4 GeV2 at t = ?1. 相似文献
16.
The branching ratio for B
s
→ ℓ+ℓ−
γ mode is of the same order as B
s
→ ℓ+ℓ−, since there is no helicity suppression in the 3-body decay mode. New Physics beyond Standard Model may affect these rates
favourably for experimental observation at LHC and simultaneous measurements of the modes B
s
→ μ+μ− and B
s
→ μ+μ−
γ at LHC experiment will indicate the basic nature of the interaction at play. A simulation study has been performed to evaluate
the potential of CMS detector to observe the more difficult mode of B
s
→ μ+μ−γ. An upper limit of 2.08 × 10−7 on the branching ratio is expected to be achieved corresponding to an integrated luminosity of 10 fb−1. 相似文献
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Xiang Liu Zheng-Tao Wei Xue-Qian Li 《The European Physical Journal C - Particles and Fields》2009,59(3):683-689
To test the validity of perturbative QCD (pQCD) and investigate its range of application, one should look for a suitable process.
B→J/ψ
D is a promising candidate. The linear momentum of the products is relatively small, so that there may exist a region where
exchanged gluons are soft and the perturbative treatment may fail, so that the non-perturbative effect would be significant.
We attribute such non-perturbative QCD effects to the long-distance final-state interaction (FSI) which is estimated in this
work. We find that the contribution from the FSI to the branching ratio is indeed sizable and may span the rather wide range
of 10−6∼10−5 and cover a region where the pQCD prediction is of the same order. A more accurate measurement of its branching ratio may
provide important information about the application region of pQCD and help to clarify the picture of inelastic rescattering
(i.e. FSI), which is generally believed to play an important role in B decays. 相似文献
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In the present paper we propose a further modification of f(R, T)-gravity (where T is trace of the energy-momentum tensor) by introducing higher derivatives matter fields. We discuss stability conditions in the proposed theory and find restrictions for the parameters to prevent appearance of main type of instabilities, such as ghost-like and tachyon-like instabilities. We derive cosmological equations for a few representations of the theory and discuss main differences with conventional f(R, T)-gravity without higher derivatives. It is demonstrated that in the theory presented inflationary scenarios appear quite naturally even in the dust-filled Universe without any additional matter sources. Finally, we construct an inflationary model in one of the simplest representation of the theory, calculate the main inflationary parameters and find that it may be in quite good agreement with observations. 相似文献